function attribute( $value ) { switch ( $value ) { case "has_content": { return eZISBN13::hasRangeData(); }break; case "groups": { $groupList = eZISBNGroup::fetchList(); return array( 'group_list' => $groupList, 'count' => count( $groupList ) ); }break; case "group_ranges": { $groupList = eZISBNGroupRange::fetchList(); return array( 'group_list' => $groupList, 'count' => count( $groupList ) ); }break; } return null; }